CVE-2026-20221 Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel…
Description
Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine. This vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| Cisco Cyber Vision 5.6 | 5.6.0 → 5.6.1 | No fix stated |
| Cisco Cyber Vision | 5.5.1 | No fix stated |
| Cisco Cyber Vision 5.4 | 5.4.0 → 5.4.2 | No fix stated |
| Cisco Cyber Vision 5.3 | 5.3.0 → 5.3.3 | No fix stated |
| Cisco Cyber Vision 5.2 | 5.2.0 → 5.2.1 | No fix stated |
| Cisco Cyber Vision 5.1 | 5.1.0 → 5.1.3 | No fix stated |
| Cisco Cyber Vision 5.0 | 5.0.0 → 5.0.2 | No fix stated |
| Cisco Cyber Vision 4.4 | 4.4.0 → 4.4.3 | No fix stated |
| Cisco Cyber Vision 4.3 | 4.3.0 → 4.3.3 | No fix stated |